LG OM7550 User manual

SERVICE MANUAL
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
Internal Use Only
Website http://biz.lgservice.com
Mini Hi-Fi AUDIO
MODEL: OM7550
MODEL: OM7550
P/NO : AFN77277076 SEPTEMBER, 2015

CONTENTS
SECTION 1 ........ GENERAL
SECTION 2 ........ CABINET & MAIN CHASSIS
SECTION 3 ........ ELECTRICAL
SECTION 4 ........ REPLACEMENT PARTS LIST
1-1

SECTION 1
SUMMARY
CONTENTS
SERVICING PRECAUTIONS ............................................................................................................................ 1-3
ESD PRECAUTIONS......................................................................................................................................... 1-5
HIDDEN KEY MODE ......................................................................................................................................... 1-6
SERVICE INFORMATION FOR EEPROM........................................................................................................ 1-7
PROGRAM DOWNLOAD & UPDATE GUIDE.................................................................................................. 1-8
1. AUDIO PROGRAM ................................................................................................................................... 1-8
2. CD PROGRAM ......................................................................................................................................... 1-9
3. EQ PROGRAM ....................................................................................................................................... 1-10
SPECIFICATIONS ........................................................................................................................................... 1-11
1-2

1-3
NOTES REGARDING HANDLING OF THE PICK-UP
1. Notes for transport and storage
1) The pick-up should always be left in its conductive bag until immediately prior to use.
2) The pick-up should never be subjected to external pressure or impact.
2. Repair notes
1) The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.
2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and
impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or
damage to the printed-circuit board.
3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason
the adjustment point and installation screws should absolutely never be touched.
4) Laser beams may damage the eyes!
Absolutely never permit laser beams to enter the eyes!
Also NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.
5) Cleaning the lens surface
If there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as used
for camera lens). The lens is held by a delicate spring. When cleaning the lens surface, therefore, a cot-
ton swab should be used, taking care not to distort lens.
6) Never attempt to disassemble the pick-up.
Spring has excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab.
(Do not use any other liquid cleaners, because they will damage the lens.) Take care not to use too much
of this alcohol on the swab, and do not allow the alcohol to get inside the pick-up.
Storage in conductive bag Drop impact
NEVER look directly at the laser beam, and don’t allow
contact with fingers or other exposed skin.
Magnet
How to hold the pick-up
Conductive Sheet
Cotton swab
Pressure
Pressure
SERVICING PRECAUTIONS

NOTES REGARDING COMPACT DISC PLAYER REPAIRS
1. Preparations
1) Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). These components
are sensitive to, and easily affected by, static electricity. If such static electricity is high voltage, components
can be damaged, and for that reason components should be handled with care.
2) The pick-up is composed of many optical components and other high-precision components. Care must be
taken, therefore, to avoid repair or storage where the temperature or humidity is high, where strong magne-
tism is present, or where there is excessive dust.
2. Notes for repair
1) Before replacing a component part, first disconnect the power supply lead wire from the unit
2) All equipment, measuring instruments and tools must be grounded.
3) The workbench should be covered with a conductive sheet and grounded.
When removing the laser pick-up from its conductive bag, do not place the pick-up on the bag. (This is
because there is the possibility of damage by static electricity.)
4) To prevent AC leakage, the metal part of the soldering iron should be grounded.
5) Workers should be grounded by an armband (1 M)
6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent
static electricity changes in the clothing to escape from the armband.
7) The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.
Resistor
(1 M)Conductive
Sheet
Resistor
(1 M)
Armband
1-4

1-5
Electrostatically Sensitive Devices (ESD)
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components
commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated
circuits and some field-effect transistors and semiconductor chip components. The following techniques should
be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off
any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a
commercially available discharging wrist strap device, which should be removed for potential shock reasons
prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive surface
such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.
4. Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static" can
generate electrical charges sufficient to damage ESD devices.
5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESD
devices.
6. Do not remove a replacement ESD device from its protective package until immediately before you are
ready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together by
conductive foam, aluminum foil or comparable conductive materials).
7. Immediately before removing the protective material from the leads of a replacement ESD device, touch the
protective material to the chassis or circuit assembly into which the device will by installed.
CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL OTHER
SAFETY PRECAUTIONS.
8. Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless motion
such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate
static electricity sufficient to damage an ESD device).
CAUTION. GRAPHIC SYMBOLS
THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS
INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED
“DANGEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE A RISK OF
ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE
SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE
LITERATURE.
ESD PRECAUTIONS

1-6
HIDDEN KEY MODE
Push both Front key and RCU key to activate it for 5 seconds.
1. Disc Lock On/Off (CD Function Only Active)
Front Key : STOP
RCU Key : STOP
2. Check Version and Option code
Front Key : STOP
RCU Key : PLAY/PAUSE
You can change [Audio MCU Version <-> CD Controller Version <-> EEPROM Option] by SKIP+/-.
3. Clear EEPROM
Front Key : STOP
RCU Key : SKIP-
4. Edit EEPROM
Front Key : STOP
RCU Key : SKIP+
You can change the digit of option by SKIP+/-.
You can edit 0~f by REPEAT or PLAY/PAUSE key.
5. Bluetooth DUT
Front Key : STOP
RCU Key : PROGRAM
Bluetooth model only
6. Power Disc Lock On/Off (CD Function Only Active)
Front Key : STOP
RCU Key : EQ
7. Amp Clip On/Off
Front Key : STOP
RCU Key : Mute
Amp Clip Mode Change (Amp Clip On --> Amp Clip Off --> Level Down display).

POWER ON
VFD “NO DISC” status
It is possible at any function.
(ex. It is possible at VFD “NO USB” status, too.)
This is an example.
Front ‘STOP’ + Remote control “ ”
push same timing during 5s
FLD “OP00-…..”
Move to appropriate position
And make changes
with RMC “ , , , REPEAT” key.
Press STOP Key
VFD “WRITE OK”
Front ‘STOP’ + Remote control “ ”
push same timing during 5s
VFD “E2P CLR”
Completed
1-7
SERVICE INFORMATION FOR EEPROM
dM

1. AUDIO PROGRAM
Download program file name must be MICOM_OM9550_YYMMDDX.HEX
If security program(Water Wall) is activated on PC, you must save the file to the USB storage device
and disable the security software, then download the file to your set.
Downloading file proceeds in the same way at USB1 function and USB2 function.
Caution: When downloading the file, you should neither unplug the USB device, change to the other function,
nor power off the device. USB device must be unplugged when the downloading process is completed.
ON VFD DISPLAY SCREEN
1) (Fast) Format USB device
2) Copy Firmware file to USB device.
NO USB
Insert USB device at USB function
SEARCH

MICOM UP

FINISH

Auto POWER OFF
1-8
PROGRAM DOWNLOAD & UPDATE GUIDE

2. CD PROGRAM
Download program file name must be HG590_OM9550_YYMMDDX.bin
If security program(Water Wall) is activated on PC, you must save the file to the USB storage device
and disable the security software, then download the file to your set.
Downloading file proceeds in the same way at USB1 function and USB2 function.
Caution: When downloading the file, you should neither unplug the USB device, change to the other function,
nor power off the device. USB device must be unplugged when the downloading process is completed.
ON VFD DISPLAY SCREEN
1) (Fast) Format USB device
2) Copy Firmware file to USB device.
NO USB
Insert USB device at USB function
SEARCH

FIRMWARE

FINISH

Auto POWER OFF
1-9

3. EQ PROGRAM
Download program file name must be EQ_PRG_OMXX50_YYMMDDX_XXXX.BIN
If security program(Water Wall) is activated on PC, you must save the file to the USB storage device
and disable the security software, then download the file to your set.
Downloading file proceeds in the same way at USB1 function and USB2 function.
Caution: When downloading the file, you should neither unplug the USB device, change to the other function,
nor power off the device. USB device must be unplugged when the downloading process is completed.
ON VFD DISPLAY SCREEN
1) (Fast) Format USB device
2) Copy Firmware file to USB device.
NO USB
Insert USB device at USB function
SEARCH

EQ UP

FINISH

Auto POWER OFF
1-10

SPECIFICATIONS
1-11
• GENERAL
Power requirements Refer to the main label.
Power consumption Refer to the main label.
Networked standby : 0,4 W
(If all network ports are activated.)
Dimensions (W x H x D) 430 mm x 765 mm x 468 mm
Net Weight (Approx.) 22.7 kg
Operating temperature 5 °C to 35 °C (41 °F to 95 °F)
Operating humidity 60 %
Bus Power Supply 5 V 500 mA
• INPUTS / OUTPUTS
AUX IN / OUT 2,0 Vrms (1 kHz, 0 dB), 600 Ω, RCA jack (L, R)
PORT. IN 1,2 Vrms (3.5 Ø jack)
MIC 20 mV
• TUNER
FM Tuning Range 87,5 to 108,0 MHz or 87,50 to 108,00 MHz
• CD
Frequency Response 40 to 20 000 Hz
Signal-to-noise ratio 75 dB
Dynamic range 80 dB
• AMPLIFIER
Total output 1000 W
FRONT 500 W x 1 (6 Ωat 150 Hz)
Subwoofer 500 W x 1 (6 Ωat 1 kHz)
THD 20 %
• Design and specifications are subject to change without notice.

1-12

SECTION 2
CABINET & MAIN CHASSIS
CONTENTS
DISASSEMBLY INSTRUCTIONS ..................................................................................................................... 2-2
1. HOW TO DISASSEMBLE THE SIDE COVER (LEFT & RIGHT) ............................................................. 2-2
EXPLODED VIEWS ........................................................................................................................................... 2-5
1. CABINET AND MAIN FRAME SECTION ................................................................................................. 2-5
2. DECK MECHANISM SECTION (DM19) ................................................................................................... 2-7
3. PACKING ACCESSORY SECTION ......................................................................................................... 2-9
2-1

2-2
DISASSEMBLY INSTRUCTIONS
Figure 1
Figure 2
Step 1) Insert JIG into groove and then raise Cover_Side with a lever(JIG) to outside direction.
Step 2) Tap(Push-silde) Cover_Side to back direction.
1. HOW TO DISASSEMBLE THE SIDE COVER (LEFT & RIGHT)
-,*

2-3
Figure 3
Step 3) Seperate Cover_Side to out direction.

2-4

2-62-5
EXPLODED VIEWS
1. CABINET AND MAIN FRAME SECTION
B
L
O
M
C
I
H
D
F
E
R
G
D
I
BC
Q
N
O
A
A
E
H
F
G
Q
P
N
L
K
P
K
J
J
M
R
MAIN
SMPS
TOP
VFD
FRONT
B/T
468
A52
255
256
257
468
468
468
263
264
265
266
267
268
270
A46
468
468
443
443
285
286
284
283
282
282
A47
443
443
443
260
262
261
A41
250
251
443
A44
254
A43
A42 443
A49
A50
275
277
276
279
512
278
252
468
512
512
512
512
443
518
518
CABLE2 CABLE3
281
512
CABLE5

1439
A001
1002
1005 1001
1049
1437
1437
1024
1024
1024
1024
1003
1011
1437
1004
1026
1030
1043
1045
A005
A006
1016
1013 1015
1020
1439
1018
1019
1012
1006
2. DECK MECHANISM SECTION (DM19AA)
2-82-7

3. PACKING ACCESSORY SECTION
2-9
825 FM Antenna
900 Remote Control
803 Packing
803 Packing
808 Batteries
801 Owner’s manual
803 Packing
802 Box
803 Packing
804 Bag
300 Power Cord